1. Field of the Invention
The disclosures herein generally relate to a liquid droplet discharge head, a liquid droplet discharge apparatus including the liquid droplet discharge head, and an image forming apparatus including the liquid droplet discharge apparatus; and particularly to a liquid droplet discharge head used in an image forming apparatus such as a printer, a facsimile machine, a copier, a plotter, or a multifunction peripheral (MFP) having more than one of the above functions.
2. Description of the Related Art
An image forming apparatus such as a printer, a facsimile machine, a copier, a plotter, or a MFP having more than one of the above functions may use a liquid droplet discharge apparatus (also referred to as “liquid discharge apparatus”) including a liquid droplet discharge head (also referred to as “liquid discharge head” or “recording head” hereinafter) that discharges droplets of recording liquid such as ink to form an image by discharging the recording liquid on a recording medium such as paper that is being transported.
To simplify the structure of such a liquid droplet discharge head and reduce its manufacturing cost, techniques related to creating a common liquid chamber for storing recording liquid such as ink by arranging multiple layers of pressed parts are being adopted especially in an inkjet head that discharges ink. (See, e.g., Patent Documents 1 and 2)
Patent Documents 1 and 2 disclose a technique for creating a common liquid chamber by layering plural metal plates and resin plates and bonding the plates together by applying adhesive to the plates and heating/pressing the plates.
Patent Document 3 discloses a technique for creating a common liquid chamber by laminating plural photosensitive resin plates.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2004-025636    [Patent Document 2] Japanese Laid-Open Patent Publication No. 2006-095884    [Patent Document 3] Japanese Laid-Open Patent Publication No. 09-295403
However, the techniques disclosed in Patent Documents 1-3 require a relatively large number of parts for creating the common liquid chamber so that a relatively large number of assembly steps are required, which leads to an increase in manufacturing costs.
That is, in the case of creating parts from a metal plate by punch pressing the metal plate, restrictions are imposed on the thickness of the metal plate in consideration of the aspect ratio so that the number of layers has to be increased in order to secure the required volume for the common liquid chamber. When the number of layers is increased, the process steps for assembling the recording head are increased in number and complexity due to the increased number of bonding faces and the need to determine the positions of each of the layers, which in turn leads to an increase in manufacturing costs.
It is noted that the aspect ratio refers to the ratio of the plate thickness to the shortest distance between adjacent punch pressed parts. If the shortest distance between adjacent punch pressed parts is less than the plate thickness, accuracy of the punch pressed product cannot be ensured. For example, when a metal plate made of steel or stainless steel (SUS) with a plate thickness of 0.5 mm is used to create two holes corresponding to adjacent punch pressed parts, the holes may not be accurately punch pressed if the distance between the holes (i.e., dimension of the portion that is not perforated) is less than 0.5 mm.